[Fixed] Invalid module name in augmentation — error while using map option for RxJs – Rxjs

The Solutions:

Solution 1: Import Statements within the Module Declaration

The solution is to move all the import statements inside the declare module "moduleName" {} block. This ensures that the module name is properly defined before the import statements, resolving the issue with the invalid module name in augmentation.

To clarify:

1. Locate the .d.ts file where you are experiencing the error.
2. Inside this file, find the section where you have the declare module "moduleName" {} declaration.
3. Move all the import statements that are currently outside the module declaration block into the block.
4. The resulting structure should look similar to this:

declare module "moduleName" {
  // import statements
  import { Observable, Subject } from 'rxjs';

  // module members
  export class MyClass {
    // ...
  }
}

By placing the import statements within the module declaration block, you are explicitly defining the module name before referencing it in the import statements, which resolves the issue with invalid module name in augmentation.

Solution 2: Using `@import` and `declare module`

To resolve the error and enable full IntelliSense in your code, you can follow these steps:

1. Add the @import statement:

   Before defining your Observable interface, add the following @import statement:

   import { Observable } from 'rxjs';
   

   This imports the Observable type from the rxjs package.

2. Use the declare module syntax:

   After importing the Observable type, use the declare module syntax to augment the Observable interface with your custom methods or properties. For example:

   declare module 'rxjs' {
     interface Observable<T> {
       // Define your custom methods or properties here
     }
   }
   

   By using the declare module syntax, you are telling TypeScript to treat the Observable interface as if it were a part of the rxjs module. This allows you to add custom methods or properties to the Observable interface without modifying the original rxjs library.

3. Ensure that your rxjs version is up-to-date:

   Make sure that the version of rxjs in your package.json is above "^5.0.0". This is because the declare module syntax is only supported in TypeScript versions 2.4 and above, which require RxJS 5.0 or higher.

By following these steps, you should be able to resolve the error and enable full IntelliSense for your custom methods or properties on the Observable interface.

Solution 3: Downgrading the TypeScript Language Service

The Visual Studio IDE uses a TypeScript language service which may not support the latest TypeScript features, such as module augmentation. As a result, you may encounter errors like "Invalid module name in augmentation".

To resolve this issue, you can downgrade the TypeScript language service:

• Open the Visual Studio options dialog.
• Navigate to the "Text Editor" > "JavaScript/TypeScript" > "Language Service" settings.
• Under the "TypeScript Language Service" section, select the "Use a specific version of TypeScript" checkbox.
• In the "Version" field, enter the desired TypeScript version. For example, if you want to use TypeScript 2.0, you would enter "2.0".
• Click the "OK" button to save your changes.

This should update the TypeScript language service and resolve the error.